1. Field of the Invention
The present invention relates to a semiconductor process. More particularly, the present invention relates to a method for removing polymer as an etching residue from a substrate.
2. Description of the Related Art
In a semiconductor process, the patterning process of a material layer usually includes a lithography step for forming patterned photoresist and an etching step using the patterned photoresist as a mask. Since the photoresist is an organic material, some polymer as an etching residue remains on the substrate after the etching step and will cause certain problems. For example, in a process of forming damascene openings, polymer as an etching residue is frequently formed on the sidewall of the openings. If the polymer is not removed with a suitable method, it will adversely affect the effect of metal filling, so that the quality of the resulting metal interconnection is degraded.
To solve the problem of polymer residue, wet clean is usually performed after the etching step. The wet clean step uses a solution containing a surfactant to wash the substrate and remove the polymer therefrom. However, in a damascene opening process using a metal hard-mask layer, incomplete removal of sidewall polymer is frequently found in the damascene openings in the central area of a wafer. Therefore, the quality of the metal interconnection structure filled in the damascene openings is greatly degraded to decrease the yield of product significantly.